1. Field of the Invention
This invention relates to an X-ray generator of a dental X-ray apparatus used for taking continuous tomograms of the dental arch of a human being and, more particularly, to an X-ray generator in which the size of the slit for emitting X-ray beams therethrough can be controlled by sheltering either or both at the upper and the lower ends of the slit with intercepting means.
2. Prior Art
The X-ray generator with an X-ray tube therein of an X-ray apparatus which has so far been used for dental purposes includes a head in front whose front-wall is provided with a slit normally elongated in the vertical direction through which X-ray beams are emitted on the surface of the X-ray film. However, the X-ray emitting slit in the prior art generator has been equipped with no means for controlling the area on which the X-ray beams would be exposed.
Therefore, the following defects should be pointed out in the prior art generator. Namely, as well known, there are two kinds of photograhic regions in taking a tomogram of the dental arch of a human being; one of which is a wide region including the head, the nose besides the dental arch, while the other of which is a narrow one covering only the dental arch. On the other hand, an X-ray film for the apparatus is commercially obtainable for each purpose respectively. Nevertheless, it has been the general practice that one X-ray generator is used for these two purposes by using the same X-ray emitting slit vertically longer sized since the wide region contains the narrow region therein. In this way, however, even in the case where only the narrow region is required, the patient is forced to be exposed to X-rays to an unnecessarily wide extent, which may result in excessive exposure of X-rays to the patient and also unnecessary consumption of the film.
Thus, in making tomograms of the dental arch, a practical solution for adjusting the vertical size of X-ray emitting slit has been strongly longed for so that only the diseased part of the patient can be exposed to X-ray without changing the generator.